1. Field of the Invention
This invention relates to a balloon catheter. More particularly, it relates to a balloon catheter for expanding and thereby remedying stenosis in a blood vessel for improving the state of the distal side blood stream.
2. Description of the Prior Art
In the event of stenosis or obturations in the vascular system, such as blood vessels, percutaneous transuminal angioplasty (PTA) or percutaneous transluminal coronary angioplasty (PTCA) is performed for enlarging or recanalizing the narrowed or obturated site of the vascular system to thereby improve the body liquid stream towards the distal side of the vascular system. In PTA or PTCA, after a blood vessel is procured percutaneously, a fine guide wire is passed through the vessel. A catheter having an end balloon (expandable member) is introduced into the vessel, using this guide wire as the guide, until the balloon is positioned at the site of lesion where stenosis or obturation has occurred. A liquid such as contrast medium is injected continuously into the balloon via an end hub under a pressure of several to ten atmospheres for dilating the balloon towards the inner wall of the blood vessel for pressuring and thereby enlarging the narrowed or obturated sites.
As a balloon catheter employed in PTA or PTCA, there is known a balloon catheter having a coaxial dual tube system including an inner tube opened at one end and defining a first lumen and an outer tube surrounding the inner tube, forming a second lumen with the inner tube and provided with a distal balloon, or one in which a tubular member defining a lumen is provided with a distal balloon surrounding the end of the tubular member.
In the case of the former balloon catheter having the coaxial dual tube system, ring markers formed of an X-ray opaque material are provided at predetermined portions of the inner tube in the balloon that are substantially in register with both ends of the balloon., these ring markers being used as means for identifying the cylindrical portion of the balloon under X-ray fluoroscopy. However, considering that the balloon catheter is caused to proceed through the inside of the blood vessel presenting acute bend or bends, the risk is high that the inner tube disposed within the balloon at the bends of the blood vessel be broken and collapsed the lumen opened at one end the lumen opened at one end to obstruct smooth progress of the guide wire.
For overcoming the above difficulties, there is also known a balloon catheter in which a piping having at both ends thereof prescribed portions substantially in register with both ends of the cylindrical portion of the balloon is provided on the inner tube disposed within the balloon. While it is possible with this known balloon catheter to prevent the inner tube from being broken and collapsed, it is difficult for the balloon catheter to proceed through the inside of the blood vessel presenting acute bend or bends. Even supposing that the balloon catheter should have succeeded in proceeding beyond the bend, the risk is high that the piping remains bent to obstruct the progress thereof the blood vessel beyond the bend towards the distal side of the vascular system.